Antimony organic sulfur-containing compounds are well known as stabilizers for vinyl halide resins to guard against degradation by heat during molding and working of the resin into useful articles. Prior art patents which disclose such antimony organic sulfur-containing compounds and their utility as stabilizers include U.S. Pat. Nos. 2,680,726; 2,684,956; 3,340,285; 3,399,220; 3,466,261 and 3,530,158. In past commercial practice, however, the antimony mercaptides have not been widely used as stabilizers because of various shortcomings including, for example, their propensity to exude from molded or worked PVC plastic stock, cost or lack of other advantages associated with their use which might outweigh such shortcomings. U.S. Pat. No. 3,887,508 is directed to improvements in the utilization of antimony organic sulfur-containing compounds in combination with metal carboxylates. As described in U.S. Pat. No. 3,887,508, the utility and efficiency of such antimony compounds are improved in the heat stabilization of vinyl halide resins to an unexpected degree. It has been observed, however, that such antimony compounds which are normally liquid tend to deteriorate or become unstable upon storage.
The problem is particularly important with respect to antimony tris-isooctyl thioglycolate which has secured NSF approval for use in pipe for potable water. Antimony tris-isooctyl thioglycolate is unstable and hydrolyzes on exposure to moisture and air and, hence, requires stabilization. Tert-butyl catechol (TBC) has been widely employed as a stabilizer for commercial antimony stabilizers. However, TBC is itself colored and has been known to react with ingredients in rigid vinyl halide formulations. Therefore, it remains an objective of the industry to provide an efficient stabilizing agent for the antimony organic sulfur-containing compounds, particularly for antimony tris-isooctyl thioglycolate.